Is it possible to see sound? Yes, but it takes some crafty photographic wizardry

The concept of ‘seeing sound’ might seem preposterous, but when you consider that sound is just compressed air travelling in waves, the idea becomes a bit more logical. The real trick is capturing air flow in a way that makes it perceptible to the human eye. Through some clever tricks, scientists are able to do just that using a technique called Schlieren flow visualisation, which is used to study everything from heat and sound to aerodynamics and the spread of disease.

Climate change science is centuries, not decades old, and it was pioneered by a woman

The notion that human activities might be warming the planet started coming into focus in the 1960s and ’70s, before a scientific consensus emerged in the 1980s and ’90s. But the rough outlines of the science surrounding humanity’s greatest contemporary threat has a surprising, little-known history that dates back roughly two centuries. This brief animation from BBC Ideas traces our modern understanding of the greenhouse effect through the work of three pioneering scientists, beginning with the US scientist and women’s rights activist Eunice Foote, whose 1856 work on the heat-trapping effects of CO₂ was buried for decades before being rediscovered in 2010.

After 30 years of solitude, Peter forms an unlikely friendship with a fellow loner

‘I had left my flock, and Ben had left his.’

After taking a walk through a remote Welsh valley, Peter committed himself to a life there, and disconnected from the outside world. In doing so, he found a solitary inner peace – a peace he maintained for nearly three decades, until, one day, he stumbled upon a lamb that had been left for dead. Finding kinship with the fellow ‘dropout’, Peter took the abandoned creature home and named him Ben. The short Peter and Ben (2007) by the UK filmmaker Pinny Grylls captures the duo’s relationship three years after their chance meeting, as Peter attempts to return Ben to the wild. With a melancholic piano score and sweeping views of the Welsh countryside, her touching film lends a lyrical beauty to this tale of unlikely connection and camaraderie between outsiders.

Trawling for secrets in haunting films recovered from the bottom of the sea

The British ocean liner RMS Lusitania embarked on its infamous final voyage from New York to Liverpool on 1 May 1915. Six days later, torpedoed by German U-boats off the southern coast of Ireland, the ship sank in less than 20 minutes, killing 1,198 passengers and crew, and setting the US on the path to join the fight against Germany in the First World War. One of the most luxurious ocean liners of its time, the Lusitania was equipped with what was then a novelty – an onboard movie theatre.

In Sunken Films, the US artist and filmmaker Bill Morrison uses archival footage to unspool the stories of the sinking of this luxury liner, its incendiary movie reels, as well as other films about or from shipwrecks. One early clip was salvaged from the sunken Lusitania in a 1982 expedition; another mysterious film, featuring the Russian revolutionary Vladimir Lenin in 1919-20 with his cat, was recovered from a fishing net off the Danish coast in 1976. By trawling for memories in deep-sea shipwrecks, Morrison offers haunting glimpses into early-20th century film and world history.

Is a red apple proof that all ravens are black? A paradox of scientific logic

Can we learn anything about what makes a raven by looking only at apples? The German-born logician Carl Gustav Hempel (1905-97) thought that, using the inductive logic that scientists rely on to prove or disprove hypotheses, you ought to be able to – but in such a way that clashes mightily with human intuition. This peculiar ripple in reasoning, which became known as ‘the raven paradox’ due to the example Hempel used to elucidate it, goes as follows:

1. All ravens are black
2. If something is not black it is not a raven
3. The fact that my pet raven is black supports the hypothesis that all ravens are black
4. The fact that my apple is red also supports the hypothesis that all ravens are black

The sequence appears to break down somewhere between the third and fourth claims. And yet, upon examination, inductive logic tells us that claim four does indeed follow. In this brief animation, Marc Lange, a professor of philosophy at the University of North Carolina at Chapel Hill, dissects why Hempel’s claim seems to hold to reason, even as it cuts against our intuitions in a way that seems unresolvable.